The second seed, who won the singles title at London 2012 with a straight-sets defeat of world number one Roger Federer, had been due to play Canadian Milos Raonic last night for a place in the quarter-finals in Toronto.
Olympic champion Andy Murray faces a battle for fitness ahead of the US Open after being forced to pull out of the ATP Rogers Cup with a knee injury.
The second seed, who won the singles title at London 2012 with a straight-sets defeat of world number one Roger Federer, had been due to play Canadian Milos Raonic last night for a place in the quarter-finals in Toronto.
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